Spacecraft charging: incoming and outgoing electrons

This paper presents an overview of the roles played by incoming and outgoing electrons in spacecraft surface and stresses the importance of surface conditions for spacecraft charging. The balance between the incoming electron current from the ambient plasma and the outgoing currents of secondary electrons, backscattered electrons, and photoelectrons from the surfaces determines the surface potential. Since surface conditions significantly affect the outgoing currents, the critical temperature and the surface potential are also significantly affected. As a corollary, high level differential charging of adjacent surfaces with very different surface conditions is a space hazard.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Ital

Motives for online gaming questionnaire: Its psychometric properties and correlation with Internet gaming disorder symptoms among Chinese people

Internet gaming disorder (IGD) imposes a potential public health threat worldwide. Gaming motives are potentially salient factors of IGD, but research on Chinese gaming motives is scarce. This study empirically evaluated the psychometric properties of the Chinese version of the Motives for Online Gaming Questionnaire (C-MOGQ), the first inventory that measures seven different gaming motives applicable to all type of online games. We also investigated the associations between various gaming motives and IGD symptoms among Chinese gamers. Methods Three hundred and eighty-three Chinese adult online gamers (Mean age = 23.7 years) voluntarily completed our online, anonymous survey in December 2015. Results The confirmatory factor analysis results supported a bi-factor model with a general factor subsuming all C-MOGQ items (General Motivation) and seven uncorrelated domain-specific factors (Escape, Coping, Fantasy, Skill Development, Recreation, Competition, and Social). High internal consistencies of the overall scale and subscales were observed. The criterion-related validity of this Chinese version was also supported by the positive correlations of C-MOGQ scale scores with psychological need satisfaction and time spent gaming. Furthermore, we found that high General Motivation (coupled with high Escape motive and low Skill Development motive) was associated with more IGD symptoms reported by our Chinese participants. Discussion and conclusions Our findings demonstrated the utility of C-MOGQ in measuring gaming motives of Chinese online gamers, and we recommend the consideration of both its total score and subscale scores in future studies

Developments in synthesis, characterization, and application of large, high-quality CVD single crystal diamond

Single crystal diamond synthesis by microwave plasma chemical vapor deposition at rapid growth rate has considerably advanced in the past few years. Developments have been made in growth, optical quality, and mechanical properties. Of the various types of single crystal diamond that can be produced using these techniques, high quality single crystal CVD diamond can be routinely produced, and this material is playing an increasing role in research on materials under extreme conditions. This article highlights recent developments in single crystal CVD diamond synthesis and characterization, as well as various applications in high-pressure materials research.За останні кілька роки синтез монокристалів алмазу мікрохвильовим плазмовим хімічним осадженням з газової фази з високою швидкістю значно просунувся. Прогрес було досягнуто у рості, оптичних і механічних властивостях. З різних типів монокристалічного алмазу, що можна отримати з використанням цього методу, регулярно виробляють високоякісні монокристалічні CVD-алмази, і цей матеріал відіграє все більш важливу роль при дослідженні матеріалів в екстремальних умовах. У даній роботі висвітлено останні досягнення в синтезі монокристалічного CVD-алмазу і дослідженні його характеристик, а також його різне застосування у дослідженні матеріалів при високому тиску.За последние несколько лет синтез монокристаллов алмаза микроволновым плазменным химическим осаждением из газовой фазы с высокой скоростью значительно продвинулся. Прогресс был достигнут в росте, оптических и механических свойствах. Из различных типов монокристаллического алмаза, которые могут быть получены с использованием этого метода, регулярно производят высококачественные монокристаллы CVD-алмаза, и этот материал играет все более важную роль в исследовании материалов в экстремальных условиях. В этой работе осветлены последние разработки в синтезе монокристаллов CVD-алмаза и исследовании его характерист

Probing flavor changing interactions in hadron collisions

The subprocess $gg \to t\bar{c}+\bar{t}c$ in the two-Higgs-doublet model with flavor-changing scalar couplings is examined at the one loop level. With perturbative QCD factorization theorem, the corresponding cross sections for hadron-hadron collisions are computed numerically. The results are applicable to the whole mass range of the weakly coupled Higgs bosons. In case we could efficiently exclude the severe backgrounds of the $t\bar{c}(\bar{t}c)$ production signal, probing the flavor-changing top-charm-scalar vertex at hadron colliders would be very promising and accessible experimentally.Comment: LaTex file, 14 pages, 8 EPS figure

Explaining the t tbar forward-backward asymmetry without dijet or flavor anomalies

We consider new physics explanations of the anomaly in the top quark forward-backward asymmetry measured at the Tevatron, in the context of flavor conserving models. The recently measured LHC dijet distributions strongly constrain many otherwise viable models. A new scalar particle in the antitriplet representation of flavor and color can fit the t tbar asymmetry and cross section data at the Tevatron and avoid both low- and high-energy bounds from flavor physics and the LHC. An s-channel resonance in uc to uc scattering at the LHC is predicted to be not far from the current sensitivity. This model also predicts rich top quark physics for the early LHC from decays of the new scalar particles. Single production gives t tbar j signatures with high transverse momentum jet, pair production leads to t tbar j j and 4 jet final states.Comment: 7 pages, 6 figures; v2: notation clarified, references adde

Effects of non-invasive brain stimulation in multiple sclerosis: systematic review and meta-analysis

Objective: The objective of this meta-analysis was to summarize evidence on the therapeutic effects of non-invasive brain stimulation (NIBS) on core symptoms of multiple sclerosis (MS). Specifically, findings from studies deploying transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) protocols were summarized in this review. Methods: We systematically searched articles published in four databases, until 31 May 2021, which compared the effects of active tDCS or rTMS with sham intervention in MS patients. We used a random-effects model for this meta-analysis. Meta-regression and subgroup meta-analysis were used to examine the effects of stimulation dose and different stimulation protocols, respectively. Results: Twenty-five randomized controlled trials (RCTs) were included in this review, consisting of 19 tDCS and 6 rTMS studies. tDCS led to a significant and immediate reduction of fatigue with a large effect size (Hedges’s g = −0.870, 95% confidence intervals (CI) = [−1.225 to −0.458], number needed to treat (NNT) = 2). Particularly, a subgroup analysis showed that applying tDCS over the left DLPFC and bilateral S1 led to fatigue reductions compared to sham stimulation. Furthermore, tDCS had favorable effects on fatigue in MS patients with low physical disability but not those with high physical disability, and additionally improved cognitive function. Finally, whereas rTMS was observed to reduce muscle spasticity, these NIBS protocols showed no further effect on MS-associated pain and mood symptoms. Conclusion: tDCS in MS alleviates fatigue and improves cognitive function whereas rTMS reduces muscle spasticity. More high-quality studies are needed to substantiate the therapeutic effects of different NIBS protocols in MS

Scalar-mediated ttˉt\bar t forward-backward asymmetry

A large forward-backward asymmetry in $t\bar t$ production, for large invariant mass of the $t\bar t$ system, has been recently observed by the CDF collaboration. Among the scalar mediated mechanisms that can explain such a large asymmetry, only the t-channel exchange of a color-singlet weak-doublet scalar is consistent with both differential and integrated $t\bar t$ cross section measurements. Constraints from flavor changing processes dictate a very specific structure for the Yukawa couplings of such a new scalar. No sizable deviation in the differential or integrated $t\bar t$ production cross section is expected at the LHC.Comment: 22 pages, 1 figure and 2 tables. v2: Corrected Eqs.(50,51,74), adapted Fig.1, Tab.1 and relevant discussions. Extended discussion of top decay and single to

Submillimeter Studies of Prestellar Cores and Protostars: Probing the Initial Conditions for Protostellar Collapse

Improving our understanding of the initial conditions and earliest stages of protostellar collapse is crucial to gain insight into the origin of stellar masses, multiple systems, and protoplanetary disks. Observationally, there are two complementary approaches to this problem: (1) studying the structure and kinematics of prestellar cores observed prior to protostar formation, and (2) studying the structure of young (e.g. Class 0) accreting protostars observed soon after point mass formation. We discuss recent advances made in this area thanks to (sub)millimeter mapping observations with large single-dish telescopes and interferometers. In particular, we argue that the beginning of protostellar collapse is much more violent in cluster-forming clouds than in regions of distributed star formation. Major breakthroughs are expected in this field from future large submillimeter instruments such as Herschel and ALMA.Comment: 12 pages, 9 figures, to appear in the proceedings of the conference "Chemistry as a Diagnostic of Star Formation" (C.L. Curry & M. Fich eds.

Small Business Investment:The Importance of Financing Strategies and Social Networks

This study examines the association between financing strategies and firm investments. Employing theory of financing constraints and literature on formal/informal financing of small businesses to investigate a set of 15,851 observations of Vietnamese small businesses in 11 years, we suggest a pecking order of financing strategies in terms of firm investments, in ascending order as follows: (a) firms using no external finance, (b) firms using informal finance only, (c) firms using both formal and informal finance and (d) firms using formal finance only. In addition, we incorporate the theory of social capital to explore the moderating effect of networking on the relationship between financing and investment. Empirical results show that networks may enhance the relationship between informal finance and firm investments but not formal finance